PSA Depletion Induces the Differentiation of Immature Neurons in the Piriform Cortex of Adult Mice.

Immature neurons are maintained in cortical regions of the adult mammalian brain. In rodents, many of these immature neurons can be identified in the piriform cortex based on their high expression of early neuronal markers, such as doublecortin (DCX) and the polysialylated form of the neural cell adhesion molecule (PSA-NCAM). This molecule plays critical roles in different neurodevelopmental events. Taking advantage of a DCX-CreERT2/Flox-EGFP reporter mice, we investigated the impact of targeted PSA enzymatic depletion in the piriform cortex on the fate of immature neurons. We report here that the removal of PSA accelerated the final development of immature neurons. This was revealed by a higher frequency of NeuN expression, an increase in the number of cells carrying an axon initial segment (AIS), and an increase in the number of dendrites and dendritic spines on the immature neurons. Taken together, our results demonstrated the crucial role of the PSA moiety in the protracted development of immature neurons residing outside of the neurogenic niches. More studies will be required to understand the intrinsic and extrinsic factors affecting PSA-NCAM expression to understand how the brain regulates the incorporation of these immature neurons to the established neuronal circuits of the adult brain.

Using pharmacokinetics and pharmacogenetics to optimize psychiatric treatments: A systematic review.

OBJECTIVE: Neuropsychiatrists often resort to drugs with broad interindividual pharmacokinetic variability metabolized by highly polymorphic enzymes such as CYP2D6 and CYP2C19. Pharmacokinetics and  pharmacogenetics offer considerable promise as techniques capable to allow individualized adjustments in treatments with psychoactive drugs. The  purpose of this study was to review the existing evidence for the application of  pharmacokinetics and pharmacodynamics to the dosing of drugs used in  neuropsychiatry. METHOD: A literature search was conducted in PubMed and Embase to find  prospective studies published between January 2000 and April 2021 that used  determination of psychotropic drug plasma levels or genotyping to improve  response to treatment or minimize adverse events in adult patients with  psychiatric conditions. MeSH terms and free search terms were used. Each  article was reviewed by two independent reviewers to ensure that they met the  inclusion criteria. A quantitative method was established to assess the  quality of the articles selected. Results: A total of 27 articles met the inclusion  criteria of which 16  used pharmacokinetic and 11 pharmacogenetic techniques.  Fifty percent of pharmacokinetic studies met the five predefined quality criteria. Eight of the 16  papers were on antidepressants; the remainder were on antipsychotics. Two of the latter did not find an association with efficacy or safety. None of the  pharmacogenetic studies met the five quality criteria. Only one of the two  studies on antipsychotics found fewer adverse events with genetics-guided  dosing in patients on CYP2D6 substrate antipsychotics. Six of the nine studies  on antidepressants found that pharmacogeneticsbased dosing improved  efficacy. CONCLUSIONS: The evidence available on pharmacokinetics and  harmacodynamics- based personalization of treatment with psychoactive drugs  is scarce. Many existing studies analyze associations between genotypes and response or toxicity but provide few data on the efficacy of  treatment individualization. The results obtained suggest the existence of  significant differences in pharmacokinetic parameters between responding and  nonresponding patients, particularly in the treatment of depression. Given that  the availability of pharmacogenetic information may be useful at the beginning  of treatment, combining both techniques could help optimize pharmacotherapy.  However, clinical trials are needed to establish  their benefits with greater accuracy.

OBJETIVO: Dentro de la neuropsiquiatría es habitual el empleo de fármacos con  amplia variabilidad farmacocinética interindividual y  etabolizados por enzimas altamente polimórficas como CYP2D6 y CYP2C19. La  farmacocinética y la farmacogenética se vislumbran como herramientas de  ayuda para conseguir un ajuste personalizado en el tratamiento con psicofármacos. El objetivo de este trabajo es revisar la evidencia existente sobre la aplicación de farmacocinética y farmacogenética en la  selección de dosis de los medicamentos empleados en neuropsicofarmacología.Método: Se realizó una búsqueda en PubMed y Embase para localizar estudios  prospectivos, publicados entre enero de 2000 y abril de  021, que utilizasen la determinación de niveles plasmáticos de psicofármacos o  genotipado para mejorar la respuesta o minimizar efectos adversos en  pacientes adultos con trastornos psiquiátricos. Se emplearon términos MeSH y  texto libre. Cada artículo fue revisado por dos revisores independientes para  asegurar que cumplían los criterios de inclusión. Se estableció un método  cuantitativo para valorar la calidad de los artículos incluidos. Resultados: Se incluyeron 27 artículos, 16 utilizaban farmacocinética y 11  farmacogenética. El 50% de los estudios de farmacocinética cumplieron los  cinco criterios de calidad predefinidos. Ocho de los 16 trabajos analizaron  antidepresivos y los estudios restantes antipsicóticos. Dos de estos 8, no  encontraron asociación con eficacia o seguridad. Ninguno de los estudios de  farmacogenética cumplía los cinco criterios de calidad. Sólo 1 de los 2 estudios  de antipsicóticos encuentra reducción de efectos adversos con dosis guiadas  por genética en pacientes con antipsicóticos sustratos del CYP2D6. Seis de los  9 estudios con antidepresivos encuentran mayor eficacia al dosificar utilizando  farmacogenética. CONCLUSIONES: La evidencia disponible sobre farmacocinética y  farmacogénetica en individualización del tratamiento con psicofármacos es escasa. Gran parte de los estudios analizan asociaciones entre genotipos y  respuesta o toxicidad, proporcionando pocos datos sobre la eficacia en la  individualización del tratamiento. Los resultados obtenidos apuntan a la  existencia de diferencias significativas en parámetros farmacocinéticos entre  pacientes respondedores y no respondedores, especialmente en el tratamiento  de la depresión. Disponer de información farmacogenética puede ser de  utilidad al inicio del tratamiento, por lo que combinar ambas técnicas podría  ayudar a optimizar la farmacoterapia, pero hacen falta ensayos clínicos para  establecer claramente su beneficio.

Maternal Motivation: Exploring the Roles of Prolactin and Pup Stimuli.

Motherhood entails increased motivation for pups, which become strong reinforcers and guide maternal behaviours. This depends on steroids and lactogens acting on the brain of females during pregnancy and postpartum. Since virgin female mice exposed to pups are nearly spontaneously maternal, the specific roles of endocrine and pup-derived signals in the induction of maternal motivation remain unclear. This work investigates maternal motivation in dams and virgin female mice, using a novel variant of the pup retrieval paradigm, the motivated pup retrieval test. We also analyse the role of prolactin (PRL) and of stimuli derived from a litter of pups and its mother, in the acquisition of maternal motivation. Experimental design included female mice in 3 conditions: lactating dams, comothers (virgins housed and sharing pup care with dams) and pup-naïve virgins. Females underwent 3 motivated-pup-retrieval trials, with pups displaced behind a 10-cm-high wire-mesh barrier. Dams retrieved with significantly lower latencies than comothers or virgins, indicating that full maternal motivation appears only after pregnancy. Although initially comothers and virgins showed no retrieval, comothers significantly improved throughout the experiment, suggesting an induced sensitization process. Lengthening exposure of comothers to the dyad pups-dam (from 2 to 5 days at the beginning of testing) had no strong effects on maternal sensitization. PRL responsiveness was analysed in these animals using immunohistochemical detection of phosphorylated signal transducer and activator of transcription 5 (pSTAT5, PRL-derived signalling marker). As expected, dams showed significantly higher pSTAT5 expression in most of the analysed nuclei. Moreover, comothers displayed significantly higher PRL responsiveness than pup-naïve virgins in the medial preoptic nucleus, even if they display similar circulating PRL levels, which are significantly lower than those of dams. Given the instrumental role of this nucleus in the relay and integration of pup-derived stimuli to facilitate proactive maternal responses, this increase in PRL responsiveness likely reflects the mechanism underlying the maternal sensitization process reported in this work. Since the analyses of maternal motivation and PRL signalling in the brain were performed in the same animals, we were able to explore correlation between both set of data. The results shed light on the neuroendocrine mechanisms underlying maternal motivation and other aspects of maternal behaviour.

Farmacocinética y farmacogenética en la optimización de los tratamientos en psiquiatría: Revisión sistemática / Using pharmacokinetics and pharmacogenetics to optimize psychiatric treatments: A systematic review

Objetivo: Dentro de la neuropsiquiatría es habitual el empleo de fármacos con amplia variabilidad farmacocinética interindividual y metabolizados por enzimas altamente polimórficas como CYP2D6 y CYP2C19. Lafarmacocinética y la farmacogenética se vislumbran como herramientasde ayuda para conseguir un ajuste personalizado en el tratamiento conpsicofármacos. El objetivo de este trabajo es revisar la evidencia existentesobre la aplicación de farmacocinética y farmacogenética en la selecciónde dosis de los medicamentos empleados en neuropsicofarmacología.Método: Se realizó una búsqueda en PubMed y Embase para localizarestudios prospectivos, publicados entre enero de 2000 y abril de 2021, queutilizasen la determinación de niveles plasmáticos de psicofármacos o genotipado para mejorar la respuesta o minimizar efectos adversos en pacientesadultos con trastornos psiquiátricos. Se emplearon términos MeSH y textolibre. Cada artículo fue revisado por dos revisores independientes para asegurar que cumplían los criterios de inclusión. Se estableció un método cuantitativo para valorar la calidad de los artículos incluidos.Resultados: Se incluyeron 27 artículos, 16 utilizaban farmacocinéticay 11 farmacogenética. El 50% de los estudios de farmacocinética cumplieron los cinco criterios de calidad predefinidos. Ocho de los 16 trabajos analizaron antidepresivos y los estudios restantes antipsicóticos. Dosde estos 8, no encontraron asociación con eficacia o seguridad. guno de los estudios de farmacogenética cumplía los cinco criterios decalidad. Sólo 1 de los 2 estudios de antipsicóticos encuentra reducciónde efectos adversos con dosis guiadas por genética en pacientes conantipsicóticos sustratos del CYP2D6. Seis de los 9 estudios con antidepresivos encuentran mayor eficacia al dosificar utilizando farmacogenética. (AU)

Objective: Neuropsychiatrists often resort to drugs with broad interindividual pharmacokinetic variability metabolized by highly polymorphicenzymes such as CYP2D6 and CYP2C19. Pharmacokinetics and pharmacogenetics offer considerable promise as techniques capable to allowindividualized adjustments in treatments with psychoactive drugs. The purpose of this study was to review the existing evidence for the applicationof pharmacokinetics and pharmacodynamics to the dosing of drugs usedin neuropsychiatry.Method: A literature search was conducted in PubMed and Embase tofind prospective studies published between January 2000 and April 2021that used determination of psychotropic drug plasma levels or genotyping to improve response to treatment or minimize adverse events in adultpatients with psychiatric conditions. MeSH terms and free search termswere used. Each article was reviewed by two independent reviewersto ensure that they met the inclusion criteria. A quantitative method wasestablished to assess the quality of the articles selected.Results: A total of 27 articles met the inclusion criteria of which 16 usedpharmacokinetic and 11 pharmacogenetic techniques. Fifty percent of pharmacokinetic studies met the five predefined quality criteria. Eight of the16 papers were on antidepressants; the remainder were on antipsychotics. Two of the latter did not find an association with efficacy or safety. None of the pharmacogenetic studies met the five quality criteria. Onlyone of the two studies on antipsychotics found fewer adverse events withgenetics-guided dosing in patients on CYP2D6 substrate antipsychotics.Six of the nine studies on antidepressants found that pharmacogeneticsbased dosing improved efficacy. (AU)

Pregnancy Changes the Response of the Vomeronasal and Olfactory Systems to Pups in Mice.

Motherhood entails changes in behavior with increased motivation for pups, induced in part by pregnancy hormones acting upon the brain. This work explores whether this alters sensory processing of pup-derived chemosignals. To do so, we analyse the expression of immediate early genes (IEGs) in the vomeronasal organ (VNO; Egr1) and centers of the olfactory and vomeronasal brain pathways (cFos) in virgin and late-pregnant females exposed to pups, as compared to buttons (socially neutral control). In pup-exposed females, we quantified diverse behaviors including pup retrieval, sniffing, pup-directed attack, nest building and time in nest or on nest, as well as time off nest. Pups induce Egr1 expression in the VNO of females, irrespective of their physiological condition, thus suggesting the existence of VNO-detected pup chemosignals. A similar situation is found in the accessory olfactory bulb (AOB) and posteromedial part of the medial bed nucleus of the stria terminalis (BSTMPM). By contrast, in the medial amygdala and posteromedial cortical amygdala (PMCo), responses to pups-vs-buttons are different in virgin and late-pregnant females, thus suggesting altered sensory processing during late pregnancy. The olfactory system also shows changes in sensory processing with pregnancy. In the main olfactory bulbs, as well as the anterior and posterior piriform cortex, buttons activate cFos expression in virgins more than in pregnant females. By contrast, in the anterior and especially posterior piriform cortex, pregnant females show more activation by pups than buttons. Correlation between IEGs expression and behavior suggests the existence of two vomeronasal subsystems: one associated to pup care (with PMCo as its main center) and another related to pup-directed aggression observed in some pregnant females (with the BSTMPM as the main nucleus). Our data also suggest a coactivation of the olfactory and vomeronasal systems during interaction with pups in pregnant females.

Cellular Plasticity in the Adult Murine Piriform Cortex: Continuous Maturation of Dormant Precursors Into Excitatory Neurons.

Neurogenesis in the healthy adult murine brain is based on proliferation and integration of stem/progenitor cells and is thought to be restricted to 2 neurogenic niches: the subventricular zone and the dentate gyrus. Intriguingly, cells expressing the immature neuronal marker doublecortin (DCX) and the polysialylated-neural cell adhesion molecule reside in layer II of the piriform cortex. Apparently, these cells progressively disappear along the course of ageing, while their fate and function remain unclear. Using DCX-CreERT2/Flox-EGFP transgenic mice, we demonstrate that these immature neurons located in the murine piriform cortex do not vanish in the course of aging, but progressively resume their maturation into glutamatergic (TBR1+, CaMKII+) neurons. We provide evidence for a putative functional integration of these newly differentiated neurons as indicated by the increase in perisomatic puncta expressing synaptic markers, the development of complex apical dendrites decorated with numerous spines and the appearance of an axonal initial segment. Since immature neurons found in layer II of the piriform cortex are generated prenatally and devoid of proliferative capacity in the postnatal cortex, the gradual maturation and integration of these cells outside of the canonical neurogenic niches implies that they represent a valuable, but nonrenewable reservoir for cortical plasticity.

The activation of NMDA receptors alters the structural dynamics of the spines of hippocampal interneurons.

N-Methyl-d-Aspartate receptors (NMDARs) are present in both pyramidal neurons and interneurons of the hippocampus. These receptors play a key role in the structural plasticity of excitatory neurons, but to date little is known about their influence on the remodeling of interneurons. Among hippocampal interneurons, the somatostatin expressing cells in the CA1 stratum oriens are of special interest because of their functional importance and structural characteristics: they display dendritic spines, which change their density in response to different stimuli. In order to understand the role of NMDAR activation on the structural dynamics of the spines of somatostatin expressing interneurons in the CA1 stratum oriens, we have studied entorhino-hippocampal organotypic cultures obtained from mice in which this interneuronal subpopulation expresses constitutively EGFP, and have imaged them in real-time. We have acutely infused the cultures with NMDA, a strong NMDAR agonist, and have analyzed the structural dynamics of somatostatin expressing interneurons, prior and after its administration. The appearance and disappearance rates of their dendritic spines increased 24h after the NMDA infusion and returned to baseline levels 48h afterwards. By contrast, their stability rate decreased 24h after the infusion and also returned to control levels 48h later. The relative density of the dendritic spines remained unaltered throughout the assay. Altogether, our results show that the activation of NMDARs can influence the structural dynamics of interneurons. This is especially important because of the involvement of these receptors in neuronal potentiation/depression and their putative role in the etiopathology of certain neuropsychiatric disorders, such as schizophrenia.

Early Social Isolation Stress and Perinatal NMDA Receptor Antagonist Treatment Induce Changes in the Structure and Neurochemistry of Inhibitory Neurons of the Adult Amygdala and Prefrontal Cortex.

The exposure to aversive experiences during early life influences brain development and leads to altered behavior. Moreover, the combination of these experiences with subtle alterations in neurodevelopment may contribute to the emergence of psychiatric disorders, such as schizophrenia. Recent hypotheses suggest that imbalances between excitatory and inhibitory (E/I) neurotransmission, especially in the prefrontal cortex and the amygdala, may underlie their etiopathology. In order to understand better the neurobiological bases of these alterations, we studied the impact of altered neurodevelopment and chronic early-life stress on these two brain regions. Transgenic mice displaying fluorescent excitatory and inhibitory neurons, received a single injection of MK801 (NMDAR antagonist) or vehicle solution at postnatal day 7 and/or were socially isolated from the age of weaning until adulthood (3 months old). We found that anxiety-related behavior, brain volume, neuronal structure, and the expression of molecules related to plasticity and E/I neurotransmission in adult mice were importantly affected by early-life stress. Interestingly, many of these effects were potentiated when the stress paradigm was applied to mice perinatally injected with MK801 ("double-hit" model). These results clearly show the impact of early-life stress on the adult brain, especially on the structure and plasticity of inhibitory networks, and highlight the double-hit model as a valuable tool to study the contribution of early-life stress in the emergence of neurodevelopmental psychiatric disorders, such as schizophrenia.

A "double hit" murine model for schizophrenia shows alterations in the structure and neurochemistry of the medial prefrontal cortex and the hippocampus.

Both alterations in neurodevelopment and aversive experiences during childhood and adolescence seem important risk factors for schizophrenia. Animal models reproducing these alterations mimic some of the symptoms, constituting a valid approach to study the etiopathology of this disorder. Among these models, the perinatal injection of N-methyl-d-aspartate receptor antagonists and the postweaning social isolation rearing are among the most widely used. Our aim is to combine them in a "double hit" model, which should produce a wider spectrum of alterations. Lister Hooded rats have been subjected to a single injection of MK-801 at postnatal day 7 and socially isolated from postweaning to adulthood. These animals presented increased body weight gain and volume reductions in their medial prefrontal cortex (mPFC) and hippocampus. They also showed an increased number of activated pyramidal neurons and alterations in the numbers of parvalbumin and calbindin expressing interneurons in the mPFC. The expressions of the polysialylated form of the neural cell adhesion molecule and GAD67 are decreased in the mPFC. The mRNA level of calbindin was decreased, while that of calretinin was increased in the mPFC. The mRNA level of ERbB4, a gene associated to schizophrenia, was also altered in this region. All these structural and neurochemical alterations, specially in cortical inhibitory circuits, are similar to those found in schizophrenic patients and are more numerous than in each of the single models. Consequently, the present "double hit" model may be a better tool to study the neurobiological basis of schizophrenia and to explore new therapeutic approaches.

PSA-NCAM is Expressed in Immature, but not Recently Generated, Neurons in the Adult Cat Cerebral Cortex Layer II.

Neuronal production persists during adulthood in the dentate gyrus and the olfactory bulb, where substantial numbers of immature neurons can be found. These cells can also be found in the paleocortex layer II of adult rodents, but in this case most of them have been generated during embryogenesis. Recent reports have described the presence of similar cells, with a wider distribution, in the cerebral cortex of adult cats and primates and have suggested that they may develop into interneurons. The objective of this study is to verify this hypothesis and to explore the origin of these immature neurons in adult cats. We have analyzed their distribution using immunohistochemical analysis of the polysialylated form of the neural cell adhesion molecule (PSA-NCAM) and their phenotype using markers of mature neurons and different interneuronal populations. Additionally, we have explored the origin of these cells administering 5'bromodeoxyuridine (5'BrdU) during adulthood. Immature neurons were widely dispersed in the cerebral cortex layers II and upper III, being specially abundant in the piriform and entorhinal cortices, in the ventral portions of the frontal and temporoparietal lobes, but relatively scarce in dorsal regions, such as the primary visual areas. Only a small fraction of PSA-NCAM expressing cells in layer II expressed the mature neuronal marker NeuN and virtually none of them expressed calcium binding proteins or neuropeptides. By contrast, most, if not all of these cells expressed the transcription factor Tbr-1, specifically expressed by pallium-derived principal neurons, but not CAMKII, a marker of mature excitatory neurons. Absence of PSA-NCAM/5'BrdU colocalization suggests that, as in rats, these cells were not generated during adulthood. Together, these results indicate that immature neurons in the adult cat cerebral cortex layer II are not recently generated and that they may differentiate into principal neurons.